The sanctions are aimed at crippling the country’s economy following President Donald Trump’s withdrawal from the 2015 nuclear deal. The measures that came into effect on Monday restore all the sanctions that had been lifted under the accord that gave Iran billions of dollars in sanctions relief in exchange for curbs on its nuclear programme.

But as the administration seeks to cut off Iran’s oil revenue it will allow some of its closest allies and rival China to continue to purchase Iranian oil as long as they work to reduce imports to zero.